Thursday, December 29, 2011

As important as your body’s physical barriers are, they can’t repel all invaders. Minor cuts in your skin open a brief, tantalizing entryway to your body’s nutrient-rich interior. Tiny germs can eventually make their way through the thickest mucous coating. And while the acid in your stomach is strong enough to pickle steel, crafty microbes can survive or slip through it to your much more hospitable intestines. (For example, H. pylori, the culprit behind most heartburn-causing stomach ulcers, secretes an acid-neutralizing enzyme that protects the microbe until it gets a chance to worm its way into your stomach walls.)
When a pathogen breaches your body’s first line of defense, the lowly foot soldiers of your immune system meet it within minutes. One of your best defenders is the macrophage (which translates as “big eater”), a swollen blob of a cell that sucks in almost any foreign particle that crosses its path, including dead cells, debris, and pathogens. Once enveloped, a battery of powerful chemicals attacks the foreign particle, destroying it in minutes. A typical macrophage may swallow some hundred bacteria before it dies, finally done in by its own toxic chemicals.

A macrophage is a type of white blood cell. All white blood cells are immune system soldiers—they simply use different tactics.

For its first strike to be successful, your body needs to respond quickly and with overwhelming force. It’s not enough to wait until wandering macrophages stumble across new invaders. Your body needs to summon its defensive forces in a hurry.

Its trick is the inflammation response, your immune system’s call to arms. Your body triggers inflammation when it detects damaged tissue, intense heat, dangerous chemicals, or potential attackers. The first effect of the inflammation response is increased blood flow—your blood vessels dilate and gaps open in your cell walls so the blood can pour into the surrounding tissue. As the blood rushes in, you feel the resulting swelling, as well as pain (because the swollen tissues press on nearby nerves that carry pain signals) and heat (because of the influx of heated blood).

The main goal of the inflammation response is to stock the affected area with your body’s immune system soldiers. In addition, the added blood increases the heat, which spurs your macrophages to work harder and can alter the delicate balance of chemical reactions in the invading pathogens, throwing them off balance. (Your body uses a fever—a sudden spike in body temperature—with much the same effect when battling more stubborn enemies.)

The only time you see your white blood cells is when pus oozes from a wound. This creamy, yellow substance contains the detritus of biological warfare—brokendown tissue cells, living and dead pathogens, and scores of dead white blood cells.

Sunday, December 25, 2011

An exhibition traces the reconstruction of a long-missing collection of writings by Archimedes

There is much cheesy lore about the ancient Greek mathematician Archimedes of Syracuse: that he popularized the word “eureka”; that he used mirrors to set Roman ships on fire; that a Roman soldier killed him in 212 B.C. while he was tracing diagrams in the sand. Not only is the lore probably untrue, historians say, but it also fails to capture the true significance of his achievements, which spanned mathematics, science and engineering and inspired the likes of Leonardo da Vinci, Galileo and Isaac Newton. Some credit him with having essentially invented the basic ideas of calculus. An exhibit opening in October at the Walters Art Museum in Baltimore will showcase a decade-long effort to restore some of his longlost texts and unearth some of his previously unknown contributions. “Lost and Found: The Secrets of Archimedes” focuses on a parchment book known as the Archimedes Palimpsest.

At one point in history, all of Archimedes’ works that survived through the Dark Ages were contained in just three tomes made by 10th-century copyists in Constantinople. One, called Codex C, disappeared some time after Western European armies sacked the Byzantine capital in 1204. Then, in 1906, Danish philologist Johan Ludvig Heiberg found a book of prayers at a monastery in the city and noticed that it was a palimpsest—meaning that the parchment had been recycled by cutting up the pages of older books and scraping them clean. Among those older books, Heiberg realized, was Codex C. Armed with a magnifying lens, Heiberg painstakingly transcribed what he could read of the older text, including parts of two treatises that no other eyes had seen in modern times. One was the “Method of Mechanical

Theorems,” which describes the law of the lever and a technique to calculate a body’s center of gravity—essentially the one still used today. Another, called the “Stomachion,” appeared to be about a tangramlike game. Soon, the book disappeared again before resurfacing in 1998 at an auction in New York City. There an anonymous collector bought it for $2 million and lent it to the Walters museum. When the palimpsest reemerged, says Will Noel, who is its curator, “it was in appalling condition.” As the exhibition will display on panels and videos, imaging experts were able to map much of the hidden text using high-tech tools—including x-rays from a particle accelerator— and to make it available to scholars. Reviel Netz, a historian of mathematics at Stanford University, discovered by reading the “Method of Mechanical Theorems” that Archimedes treated infinity as a number, which constituted something of a philosophical leap. Netz was also the first scholar to do a thorough study of the diagrams, which he says are likely to be faithful reproductions of the author’s original drawings and give crucial insights into his thinking. These will be on display, but the studies go on. Netz is now transcribing the texts contained in the palimpsest, which he estimates at about 50,000 words, most written in a shorthand typical of medieval copyists. He plans to publish a critical edition in the original Greek. “It will take probably several decades to translate it into English,” he says.

Wednesday, December 21, 2011

It’s the question that everyone seems to ask. And if you follow the standard advice (drink 8 to 10 glasses of water every day), your next request will be for directions to the restroom. Because unless you’re a strenuous exercise or a desert dweller, you’re unlikely to need that much water—and unless you’re carrying a horse’s bladder, you won’t hold onto it for long.

No one’s quite sure where the 8-to-10 glasses factoid started. However, medical professionals do agree on quite a few things about fluids:

• Six glasses is usually enough. If you must count, 6 glasses of water a day is probably a good rule of thumb (not a bare minimum). But the average person, doing gentle activity in a gentle climate, can probably get all the fluid they need from solid food alone (although it’s not recommended).

• Follow your thirst. Your need for water varies greatly depending on your activity level. Fortunately, your body is surprisingly good at telling you when to drink. And the idea that we’re chronically (and unknowingly) dehydrated is little more than science fiction.

• Don’t fear coffee and tea. Despite the diuretic properties of caffeine, you’ll still retain a large amount of the fluid in every cup—and even more if you’re a regular drinker of caffeinated beverages.

• Dehydration may worsen constipation. If you’re straining to pass stool, you might benefit from increasing your water intake a bit. However, results vary, and a more likely cause of constipation is inadequate fiber in your diet.

So why are we so easily misled by drinking myths that don’t hold water? Quite simply, in the era of modern science, we’re used to hearing (and accepting) startling facts. But when it comes to water, medical research is in an unusual position: proving that our common sense was right all along.

Friday, December 16, 2011

Probiotics are live microorganisms (bacteria or yeast) that are particularly well-suited to your digestive system. For example, lactic acid bacteria is a common probiotic that gives sourdough and yogurt their characteristic sour flavor. In your colon, lactic acid bacteria digest the sugar known as lactose and may even prevent inflammation and inhibit cancer.

However, there’s a catch. As you’ve seen, your large intestine is quite far down in your digestive system. For a probiotic to make it to its new home, it needs to pass through the inhospitable acidic environment of your stomach. Pharmaceutical companies are experimenting with special coatings that help probiotics make the hazardous journey intact, but in the meantime it’s hard to tell how effective probiotic-fortified foods really are.

Prebiotics are substances that your healthy, colon-dwelling bacteria like to munch on. Supply these bacteria with more prebiotics, and you can encourage a small population to grow. Prebiotics are naturally present in fruits and vegetables, but don’t expect to find any in a box of macaroni and cheese.

The bottom line is that both probiotics and prebiotics are based on valid nutritional science that recognizes the value of good gut bacteria. But their success as products is less clear, and it’s a good guess that you’ll get more benefit from a diet that emphasizes fruits and vegetables than one that focuses on convenience foods and nutritionally fortified drinks, no matter what miraculous new additives manufacturers toss in.

Tuesday, December 13, 2011

The steel plates worn by medieval soldiers may have led to their wearers’ demise

On August 13, 1415, the 27-year-old English king Henry V led his army into France. Within two months dysentery had killed perhaps a quarter of his men, while a French army four times its size blocked escape to Calais and across the English Channel. Winter approached; food grew scarce. Yet in one of the most remarkable upsets in military history, a force of fewer than 7,000 English soldiers— most of them lightly armed archers—repulsed 20,000 to 30,000 heavily armored French men-at-arms near the village of Agincourt, killing thousands. Shakespeare’s play Henry V attributed the victory to the power of Henry’s inspirational rhetoric; the renowned military historian John Keegan has credited the self-defeating crush of the French charge. But a study by exercise physiologists now suggests a new reason for the slaughter: suits of armor might not be all that great for fighting.

Researchers at the University of Leeds in England placed armor-clad volunteers on a treadmill and monitored their oxygen consumption. The armor commonly used in the 15th century weighed anywhere from 30 to 50 kilograms, spread from head to hand to toe. Because of the distributed mass, volunteers had to summon great effort to swing steel-plated legs through each stride. In addition, breastplates forced quick, shallow breaths. The researchers found that the suits of armor doubled volunteers’ metabolic requirements, compared with an increase of only about 70 percent for the same amount of weight carried in a backpack.

Of course, medieval battles did not happen on treadmills. The fields at Agincourt were thick with mud, having recently been plowed for winter wheat and soaked in a heavy October shower. The French charged across 300 yards of this slop, all while suffering fire from the English archers. Combine the effort required to run in armor with that needed to slog through mud, says Graham Askew, one of the study’s leaders, and you’d expect at least a fourfold increase in energy expenditure—enough, it seems, to change history.

Thursday, December 8, 2011

If you’re a citizen of the world, you’ve probably met up with that uncomfortable phenomenon known as traveler’s diarrhea—a short episode of diarrhea that strikes thosebrave enough to visit local places and enjoy local cuisine. The odd part is that traveler’s diarrhea seems to affect only travelers. Native people can eat the same foods and emerge unscathed.

The first thing to understand is that traveler’s diarrhea needs a certain level of sanitary sloppiness to occur. In particular, it only happens if there’s some way for bacteria to pass from another person’s (or an animal’s) feces into your environment. For this reason, traveler’s diarrhea happens much less often to visitors of most first-world countries. (Although Mexicans do occasionally get diarrhea when visiting the U.S., which they call“Washington’s Revenge.”)

However, this doesn’t explain why locals have a much-reduced rate of diarrhea. The answer is that, because of near-continuous exposure, their digestive systems have gradually grown to recognize and tolerate strains of bacteria that other people can’t handle. No one knows how long this immunity takes to develop or how long it holds up, but a study in Nepal found that American adults needed 7 years of local life to adjust, and they lost their tolerance after only a few months back home.

Interestingly, enterprising travelers can use one approach for instant immunity. If you’re worried about E. coli (which is the most common culprit in Mexico), you can buy a vaccine called Dukoral that gives you temporary immunity. To get Dukoral, head to your local pharmacy or check with a travel clinic, which can also identify the gastrointestinal dangers in different parts of the world.

Tuesday, December 6, 2011

During 2011’s deadly onslaught of earthquakes, floods and tornadoes, countless buildings had to be evacuated while workers checked to make sure they were stable. The events served as a reminder that most structures are still inspected by a decidedly low-tech method: the naked eye. To speed the process and make it more accurate, investigators are researching electronic skins, evolutionary algorithms and other systems that can monitor the integrity of bridges, buildings, dams and other structures in real time. To automatically detect tiny faults and relay their precise locations, civil engineer Simon Laflamme of the Massachusetts Institute of Technology and his colleagues are devising a “sensing skin”—flexible patches that glue to areas where cracks are likely to occur and continuously monitor them. The formation of a crack would cause a tiny movement in the concrete under a patch, causing a change in the electrical charge stored in the sensing skin, which is made of stretchable plastic mixed with titanium oxide. Every day a computer attached to a collection of patches would send out a current to measure each patch’s charge, a system that Laflamme and his colleagues detail in the Journal of Materials Chemistry

Another engineer is applying a similar concept to bridges. To monitor deterioration inside suspension bridge cables, Raimondo Betti of Columbia University and his collaborators are testing 40 sensors in cables in New York City’s Manhattan Bridge (above). The sensors track temperature, humidity and corrosion rate.

Although these sensors can detect damage that occurs after they have been installed, what about damage a structure had beforehand? Roboticist Hod Lipson of Cornell University and his colleagues have developed a computer model that simulates an intact structure and runs algorithms that evolve this model until it matches data that sensors provide, which can reveal a broader scope of damage.

Others are not yet convinced of these projects’ benefits. “There does not exist, yet, enough research and data that economically support continuous and timely maintenance,” Laflamme says. Another concern might be the yet to be studied long-term performance of the systems, especially in harsh environments—a matter for future research.

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In its broadest sense, science (from the Latin scientia, meaning "knowledge") refers to any systematic knowledge or practice. In its more usual restricted sense, science refers to a system of acquiring knowledge based on scientific method, as well as to the organized body of knowledge gained through such research.

Fields of science are commonly classified along two major lines: natural sciences, which study natural phenomena (including biological life), and social sciences, which study human behavior and societies. These groupings are empirical sciences, which means the knowledge must be based on observable phenomena and capable of being experimented for its validity by other researchers working under the same conditions.